Soundproof wall structure



Aug. 12, 1941. w. EGLINTON ETAL SOUNDPROOF WALL STRUCTURE Original FiledMarch 31, 1936 9/ W M G J M Z a r N MN W M W Q N u 2 5C 1 w 5 W a W m 7A J a J a w H W/mMM Patented Aug. 12,1941

SOUNDPROOF WALL STRUCTURE William Eglinton, Reseda, and Harry GailCunningham, Los Angeles, Calif., assignors to Radio Corporation ofAmerica, a corporation of Delaware Original application March 31, 1936,Serial No. 71,864. Divided and this application August 2, 1938, SerialNo. 222,628

4 Claims.

The present invention relates to camera blimps and more particularly tothe sound-proof wall structure thereof, this application being adivision of our co-pending application S. N. 71,864, filed March 31,1936, entitled Camera blimps, which has now matured into Patent No.2,179,817, dated November 14, 1939.

The invention involves a novel wall construction which providesefiicient sound insulation as well as a sturdy and rugged structurereadily adaptable to different forms and shapes. Although providing thenecessary stiffness to maintain its form, it does not have a diaphragmeffect found in the stiffening components of other types of sound-proofwalls. The stiffening element of the present invention involves a weldedskeleton of wire-mesh, the interstices of which are filled with acousticplaster. Upon this stiffening member are applied alternate layers offelt and rubber with finally a layer of leatherette, upon which acoating of lacquer is applied. Because of its excellent sound-insulatingproperties and formability, this construction is particularly suitablefor picture camera blimps to prevent the noise of the enclosed motor andcamera mechanism from reaching the associated microphone.

An object of the present invention, therefore, is to provide a moreefficient and efficacious sound-proof wall structure.

Another object of the invention is to provide a camera blimp having asound-proof wall structure with the required stiffness andsound-insulating properties.

Another object of the invention is to provide a vibration insulatedsupport for a motion picture camera and its associated blimp.

Although the novel features which are believed to be characteristic ofthis invention are pointed out with particularity in the claims appendedherewith, the manner of its organization and the mode of its operationwill be better understood by referring to the following description readin conjunction with the accompanying drawing forming a part thereof, inwhich Fig. l. is a perspective view from the rear right-hand corner of ablimp constructed of the sund-pr0of material of the invention;

Fig. 2 is a detailed sectional view of the construction of one ofthe-lower corner supports for the camera within the blimp; and

Fig. 3 is a cross-sectional view of the new sound-proof wall material.

Referring now to the drawing, the blimp casing shown in Fig. 1 comprisesa section 4 and a section 5 hinged at 6 and secured together by the base9.

clamps, one of which is shown at l. The section 4 is afiixed to the baseplate 9 by means oi. screws In, this base plate, of course, beingsupported v upon the customary motion picture camera tripod (not shown).

In Fig. 2, one of the supporting corners of the camera is shown incross-section to illustrate the manner of insulating the supporting baseplate 9 from the camera. The body of the camera support 40, carryingways 4| for the camera, is secured to a metallic member 42 by screws 42'while a further metallic member 43 is secured to An additional metallicelement 44 corresponding in configuration to the spaces between theelements 42 and 43 is located midway between them, but separatedtherefrom by layers of rubber'45 and 46. The layer of rubber 45 isinterposed between the members 43 and 44, while the similar layer ofrubber 46 is interposed between the members 40 and 44. This type ofinterdigitated, insulated joint prevents the vibrations of the camerafrom being transmitted to the base, and, consequently, to the tripod toproduce noise which might reach the microphone.

Referring now to Fig. 3, the specific type of wall construction whichhas been found to be particularly useful for a blimp of the type shownin Fig. 1 is disclosed. The stiffening component of the wall mentionedabove is composed of zigzag steel members which are welded together toform a skeleton mesh 50. The interstices of the skeleton 50 are filledwith acoustic plaster, one preferred form of which is ground-up spongecemented together with rubber cement. This sponge is of the well knowntype sold for household use. The filled mesh 50 is lined on the interiorwith a layer of rubber 5i and an innerlining of felt 52. Continuing nowtoward the outer portion of the wall, there is first applied to the mesh50 a layer of felt 53, then a layer of rubber 54, another layer of felt55, a further layer of rubber 56, a third layer of felt 51 and finally alayer of leatherette 58 covered by a coating of lacquer 59. Thislaminated wall construction provides remarkably effective soundinsulation for keeping the noises of the camera entirely within theblimp. This sound-proof or sound-insulating wall construction isparticularly eflicient not only because of its alternate layers of feltand rubber forming a combination of high efficiency, but for its meshwire skeleton filled with the acoustic plaster. This type of stiffeningelement is aperiodic and not resonant to any particular frequency ofvibration, such as the usual type of stiffening elements of other ed inthe upper half of the casing with a supply reel. Through the opening H,which is closed by a door l2 having a latch handle l3 thereon, is seen abelt l5 and a pulley I 6 which couple the motor with the tapeup reel.The door I2 has a window l8 therein for viewing the operation of thetakeup mechanism.

The motor 20 is seen through an opening 2| closed by a door 22 securedbya clamp-andhandle combination 23. Various operating camera l'evers areshown extending through the rear portion of the blimp, while the rear ofa finder is shown at 25. Some of the actuating elements shown arebuttons 21 and 28 used to insert appropriate filter glasses before thefilm in the camera, and buttons 30 and 3| for controlling the dissolvemechanism of the camera. Knob 32 controls theshutter setting of thecamera; knob 33 controls the magnification of the focusing device of thecamera, while handle 36, which is latched by a button 35, is for movingthe camera laterally from the "taking to the focusing position and viceversa. The connections of these control elements with the camera areshown in detail in the above-identified parent application, it beingnoted, however, that means are provided for disconnecting the interiormechanism'with the exterior control elements during operation of thecamera to prevent vibrations from being transmitted by the connectionsthrough the blimp Walls.

The manner in which the casing conforms to the various portions of theinterior mechanism is to be noted as well as the smoothness of thevarious corners, this being possible by the use of the above-describedwall structure.

We claim:

1. In a sound-proof structure, a supporting frame comprising a wire-meshskeleton, soundabsorbing material in the interstices of said wiremesh, alayer of rubber and an adjacent inner layer of felt on one side of saidframe, a plurality of alternate layers of felt and rubber on the otherside of said frame, and an external layer of leatherette covered by acoating of lacquer.

2. In a sound-proof structure, a wire-mesh skeleton for forming andmaintaining the shape of said structure, a sound-absorbing material inthe interstices of said wire-mesh, and a layer of rubber and felt on oneside of said mesh, and a plurality of alternate layers of felt andrubberon the other side of said mesh.

3. In a sound-proof structure, a wire-mesh skeleton for forming andmairtaining the shape of said structure, a sound-absorbing material inthe interstices of said wire-mesh, a layer of felt and rubber attachedto said wire-mesh on the interior of said enclosure, and at least fivealternate layers of rubber and felt on the exterior of said wire-mesh.

i. In a sound-proof structure, a wire-mesh skeleton having theinterstices thereof filled with ground-up sponge bound together withrubber cement to form a supporting frame, a plurality of alternatelayers of sound-absorbing material having different sound absorbingcharacteristics for covering said skeleton on one side, and alargerplurality of alternate layers of similar material coveringthe other sideof said skeleton.

' WILLIAM EGLINTON.

HARRY GAIL CUNNINGHAM.

